Fused sectionalized condenser



INVENTOR A'TTORNEY 1926 2 Sheets-Sheet l lll Raz/ph E. Marbury Sept. 15,1931. R. E. MARBURY FUSED SECTIONALIZED CONDENSER Original Filed June 16WITNESSES:

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Sept. 15, 1931. R. E. MARBURY FUSED SECTIONALIZED CONDENSER OriginalFiled June 16 1926 2 Sheets-'Sheel 2 WITNESSES:

INVENTQR Ralph E. Marbury ATTRNEY Patented Sept. 15, 1931 UNITED STATESPATENT OFFICE RALPH E. MARBURY, OIF WILKINSBURG, PENNSYLVANIA, ASSIGNORT WESTING- HOUSE ELECTRIC MANUFACTURING COMPANY, A CORPORATION 0FPENNSYL- VANIA FUSED SECTIONALIZ-ED OONDENSER Application led .Tune 16,1926, Serial No. 116,273. Renewed February 3, 1931.

My invention relates to electrostatic condensers and methods of makingthe same, and it has particular relation to paper condensers of theoil-impregnated type.

A more particular object of my invention is to provide a constructionand a method of manufacture of the condenser, whereby the labor ofreclaiming they good material out of defective condenser units isreduced to a minimum, and yet, at the same time, the amount of materialwasted in the process of manufacture is also very much reduced, ascompared to any constructions and processes of manufacture heretoforeknown and practiced. 4

With the foregoing and other objects in view, my invention consists inthe details and methods of construction hereinafter described andclaimed, with reference to the accompanying drawings, wherein Fig. 1 isa plan view of a 2% k. v.a., 220 volt condenser embodying my invention,

Fig. 2 is a side elevation thereof,

Fig. 3 is a top plan view of a single section of the condenser shown inFigs. 1 and 2, and

Fig. 4 is a side elevation of the section shown in Fig. 3.

A condenser constructed in accordance with my invention comprises alarge number of relatively small units or sections l which are oassembled, With individual fuses 2, Within a single enclosing tank 3,wherein thewhole assembly is vacuum-treated and impregnated with oil 4through a suitable opening 5 in the top of the tank.

In the process of manufacture, the individual sections are wound, in awell known manner, on a mandrel 6 of fish paper or other insulatingmaterial, t-wo aluminum foils 7 and 8 being utilized for this purpose,and

separated by three sheets 9 of paper of .0004

inches thickness each. During the winding process, two terminal strips10 and 11 are inserted into the wound structure in contact with the twofoils 7 and 8, respectively.

The fuses 2, previously mentioned, are cemented to the top end of themandrel 6, which extends beyond the wound structure of foil and paper. Aconvenient method of cementing the fuse material 2 is to first apply acoating of shellac to the mandrel and then apply the fuse materialitself, which is composed of extremely thin tin foil. The terminalstrips 10 and 1l are held in place and electrically connected to the tinfoil fuses 2 by means of eyelets 12 which are clamped, in each instance,through the mandrel, the fuse and the terminal strip. In the form of myinvention shown in Figs. 3 and 4, two fuses are shown for each condensersection, but it is obvious that only one fuse may be employed, withoutdeparting from the essential features of my invention.

Two terminal leads 14 of flexible wire are provided for each of thecondenser sections, the same being secured to the ends of the respectivefuse foils 2 by means of additional eyelets 15 which clamp the leadwires 14 in place against the fuses. After the fuse foils have beencemented' in place, holes 16 may be punched through both the mandrel andthe fuses in order to reduce the cross-sectional areas of the fuses toany desired extent, thereby avoiding the necessity of handling fusestrips .of extremely narrow width, as well as thickness, during theassembly.

It has heretofore been customary to prepare condensers in sectionalform, but not in such small sections that each section is of a verysmall capacity as comparedto the capacity of the whole, so that one ormore sections might be disconnected without greatly changing the ratingof the condenser, as is the case in my present invention. f

It has also been, to some extent, the practice to subject the individualcondenser sections to certain tests, immediately after their assembly asindividual condenser sections, said tests being for the purposeofdetecting outstanding faults, as where the'two leads or terminalstrips have been ,connected to the same sheet of foil, or .where thefoil has been wound in such manner as to project -out at the end, orwhere the paper has been damaged. Such tests cannot be Avery severebecause the water has not been taken out ofthe insulation and the lossesare very high. Furthermore, the break-down voltage of the unimpregnatedpaper dielectric is very much lower than in the final treated andimpregnated condenser.

For the reasons just mentioned, my condenser' sections 1 are tested, indry form, 1m-

mediately after the Winding of the same,

thereby culling out a certain amount of defec- 5 tive material.

The individual sections 1 are then assembled in the container 3, beingheld in position by means of clamping plates 18.

The number of sections in each assembly is somewhat larger than thenumber that is required to provide the rated capacity of the condenser.The extra condenser sections are necessary because of the impossibilityof testing the dry condenser sections under actual Working conditionsand because of failures Which may be produced by a mechanical movementor shifting of the layers of paper during the handling and compressingoperations incident to the assembly of the sections in the container 3.

The respective leads 14 of the sections are connected together to twocondenser terminals Q which are suitably mounted in insulating bushings21, extending through the top Y 22 of the condenser tank. 3. The tank isthen carefully soldered all around in order to make the same vacuum andoil-tight.

The finished condenser is then given an impregnation treatment, whichusually includes 100 hours treatment under vacuum before admitting theimpregnating fluid 4, which is a high grade of oil, preferably one whichis Huid at all operating temperatures. When the treatment just describedis completed, the tank is closed by means of the sealing plug and thecondenser is given its final test at a voltage higher than its ratedvoltage, whereby some of the condenser sections Which may have defectsare caused to 40 fail, thereby blowing their individual fuses anddisconnecting the same from the assem- `bly,as provided for in the extrasections ineluded in the unit.

The savings effected by my construction and method of manufacture willbest be unvolt condensers. and by a consideration of some of theproblems encountered in the de-l sign of electrostatic condensers.

The making of a 5 k. v. a., 220 volt unit was an extremely difficultproblem because of the extremely small number of layers of paper in eachdielectric and because of the extreme 'ly large area of dielectric whichis required. It is not possible to obtain paper having fewer than about40 conducting particles per square foot. The conductingparticles justmentioncd are of microscopic dimensions and are caused by carbon andmetallic dust in the air,

the Wearing of the calenders, and other causes. Efforts have been made,'in cooperation With paper manufacturers, to eliminate the conductingparticles, but so far, no practical solution has been obtained. Inaddition to the conducting particles, most paper contains a certainnumber of perforations. In fact, the lpaper must have a certain numberof extremely `ine `perforations in order to render it impregnable, butsome of the perforations are larger than others. As thinner and thinnermaterial is used, the problem of holes in the paper becomes stillgreater.

Heretofore 2300-volt condensers have been constructed utilizing 10sheets of L15-mil paper. Thus, each dielectric was composed of tensheets of paper, and the probability of obtaining an alinement of holesor conducting particles through all ten sheets of paper was quiteremote., A 5 k. v.a., 2300-volt condenser contained 38,000 square inchesof dielectric, each dielectric being ten sheets thick.

A 5 k. v. a., 220-volt condenser, according to my present invention,contains dielectrics comprising only 3 sheets of O l-mil paper, and thecondenser contains 432,000 square inches of dielectric, the dielectricbeing three sheets thick. By reason of the smaller number of sheets ineach dielectric, and the smaller thickness of each sheet, a far largerpercentage of `failures should be expected than Were obtained in the2300- volt condenser.

The 2300-volt condenser, With the most careful construction, involves aloss of 6% of the linal condenser units, even after the defectivematerial had been culled out as Well as was possible in the sectionalconstruction before the final assembly. Six failures out of every 100condensers of 23004 volt rating Would mean six failures out of every3,800,000 lsquare inches of dielectric, or one short-circuit in about600,000 square inches of dielectric. In making 100 condensers of the220-volt rating, there lWouldbe 43,200,000 square inches of dielectric,and 72 defects Would be expected out of 100 condensers, or 72% scrap,even if it be assumed that the percentage of defective material Would beno higher than in the 2300- volt unit. As a matter offact, however, thenumber of alinements of defects in the paper, per unit area, would bevery much greater in the 220-volt unit than in the 2300- volt unit, andhence, if the same methods of construction Were utilized in both, everyone of the 220-volt condensers would fail. Consequently, it has beenimpractical to build 5 k. v. a 220-volt condensers heretofore.

a Wound construction `of: the individual sections Would have beenpreferred, it Was neces- The actual labor of building a 2300-voltconstruction necessitated soldering the al` ternate sheets of foil,which projected at opposite sides of the condenser section, and as nokind of soldering flux could be utilized without harming the paper, itwas necessary to utilize lead foil with a stacked construction in the2300-volt unit. j

It will be clear, from the foregoing, that even though a sectionalconstruction was utilized for 220-volt condensers and even though thesections were sub-divided into as small units as possible, and eachYunit was tested as well as was possible in the dr)7 state, beforeassembling the sectionsinto their iinal'structure, there would be atleast one or two failures in each one of the ron densers, afterfinishing the compressing,

evacuating, and impregnating processes, to

say nothing of the large restacking cost. These failures are unavoidableby reason of alinement of defects in paper and the law of probabilities,whereby it was certain that some failure would be encountered throughoutthe'enormous area of dielectric which was required in the condenser.

. The occurrence of faults in the final assembly could theoretically beavoided by pressing each of the condenser sections in a tank of its,own, impregnating the same under the final pressure at which it wouldalways operate, and testing each section -so constructed, beforeassembling it in the finall condenser bank. Such method, in fact, is themethod heretofore employed for building up a condenser bank of largerating from small complete sections which are merely connected togetherin parallel to a common bus, a fuse i or other protective device beingsometimes provided for eachunit. The sections, how ever, had all beentested at a voltage higher than their rated voltage, and the fuses werenot expected to blow, in normal service, during a reasonable life of theapparatus.

The cost of a 5 k. v. a., or even a 2 k. v. a assembly of small,complete 220volt condenser units, each unit having a small rating suchas 1/8 k. v. a. or 1/25 k. v. a.,would be quite prohibitive, as comparedto the cost of a condenser constructed in accordance with my invention.The principal reason for the very high cost of the bank of smallcondenser units is the cost of impregnation. Insulation, if worked at200 to 225volts per mil in order to keep the size and cost of thecondenser unit within reason` must be of the oil-impregnated type. Eachimpregnating process requires about 100 hours, thereby imposing acertain fixed charge .for each condenser, regardless of the size of theunit. In addition, each unit must be provided with a container which isoil-tight and vacuum tight. Obviously, the cost of'such a container fora small fractional k. v. a. condenser would be a very large proportionof the total cost of the condenser.

According to my invention, the necessity for individual impregnatingtreatments and individual tanks for the several sections is avoided,thus making possible a much more elaborate evacuating, impregnating andtank-soldering treatment. If, according to the law of averages, twofailures were veX- pected for each complete condenser, each condenserwould contain two more sections than are really required, and two of thesections would be disconnected, by their fuses, upon the iinal test ofthe unit, at a suitable over-voltage, before the shipment of thecondenser.

If desired, three or four additional units may be provided in eachcasing, and the final test voltage, which is" applied before shipment,may be gradually increased to even higher values, until a sulicientnumber vof sections fail to bring down the rating to the required value,thereby producing a very superior product by virtue of the Higherstandard test.

It will be understood that the individual fuses of the sections are notexpected to blow during normal service, at the rated voltage of thecondenser, but are merely placed inside the tank for vthe purpose ofavoiding the scrapping of every condenser which is manufactured. It willbe observed that instead of having a 6% scrap of the final product, wehave no scrap whatever in the final product, the only scrap being thenormal scrap on the wound sections.

The problem of providing a fuse which would operate under oil was a.very difficult one. A fine filament could be utilized, such as are usedin lamps, but such filaments would be extremely costly to handle andwould be subject to a large amount of breaking, both in assembly and asa result of their mechanical weakness and their inability to withstandthe jars incident to the shipment of the apparatus. VIf a. foil isutilized for the fuse, it must be of eXtreme thinness, such asone-quarter of a mil, and even then, it would have to be cut afterassembly, because of the impossibility of handling such narrow` stripsas would be required.

Moreover, the cooling effect of the oil, in contact with both sides ofthe fuse strip, has a very great effect upon the magnitude of thecurrent necessary to fuse a strip of any given cross-sectional area. .Inview of the foregoing diiiiculties, it will be perceived that one of theimportant problems to be solved in the construction of my new condenserwas the provision of a fuse which is strong mechanically, is inexpensiveto handle and assemble, and is capable ofiblow- .ing at a current whichis suiciently low not to damage the entire condenser unit, even in spiteof the cooling eiect of the oil.

While I have described my invention with particular reference toa220-volt condenser, it is obvious that the same constructions andmethods of manufacture are applicable to condensers of allvoltageratings,

I claim as my invention:

1. A fused, sectionalized, impregnated i electrostatic condensercomprising a plurality of sections, an individual fuse for each section,an-impregnating fluid surrounding said fuses and said sections, and alsingle I erable, at the rated voltage of the condenser, without blowingtheir fuses. 2. A fused sectionalized, impregnated electrostaticcondenser comprising a large number of relatively small sections, eachsection being of a very small capacity as com-o .tion being wound uponan insulating man pared to the capacity of the whole, an individual fusefor each section, an impregnating fluid surrounding said fuses and saidsections, and a single-l container permanently containing saidimpregnating lfluid and the entire assembly of condenser sections withtheir individual fuses, the number of sections being somewhat largerthan the number of operative sections finally desiredto obtain the ratedcapacity, a relatively small number of sections beingrbrolien down andtheir `fuses blown prior to the actual use of the device, the remainingcondenser sections being operable, at the rated voltage of thecondenser, without blowing their fuses. 3. A fused, sectionalized,impregnated electrostatic condenser comprising a plurality of conductingsheets separated by a dielectric comprising a relatively small number ofl ers of im regnable insulatiii material ay p n g condenser whichcomprises assembling small.

of very large area, said conducting sheets and dielectric beingsubdivided into a large number of relatively small sections, eachsecdrel having an end extending beyond the wound material, a fuseconnected to the eX- tending end of each mandrel, a terminal stripsecured to said .extending end for making ing sheets wound on eachmandrel, a terminal lead connected to the aforesaid terminal strip ofeach section', in series with said fuse, a terminal strip and a'terminallead for the other of the alternate conducting sheets wound on'eachmandrel, a single. body of impregnating material for the entire assemblyof condenser sections with their individual fuses and'terminal leads,and a single permanent container therefor, the number of sections. beingsomewhat larger than the number ofoperative sections finally desired toobtain the rated capacity, a relatively small number of sections beingbroken down and their fuses blown prior to the actual use of the device,the remaining condenser sections being operable, at the rated volt-:fige of the condenser, without blowing their uses.

4. An electrostatic condenserelement comprising an insulating mandrel, apair of alternate conducting sheets separated by sheet di-4 electricmaterial wound thereon, said mandrel having an end .extending beyond theWound material, a fuse supported by the extending end of each mandrel, aterminal strip secured to said extending end for making connection withone of the alternate conducting sheets, a terminal lead connected tosaid mandrel and to said terminal stripin series with said fuse, aterminal strip and a terminal lead for theother of said alternateconducting sheets, a container for the whole assembly, and animpregnating material covering said condenser element and fuse in saidcontainer.

5. A vcondenser comprising an insulating support, a plurality ofcondenser platesl mounted on said support, a terminal secured to saidinsulating support and connected toonel of said condenser plates, asecond termin'al secured to said insulating support, and

a fuses-trip cemented to said insulating support and connecting the saidterminals.

. 6. A condenser comprising an insulating tainer for the vwholeassembly, and an impregnating material in said container.

7. The method .of making an electrostatic section, testing the saine toeliminate certain defective sections and assembling a plurality of such.tested sections, with an individual fuse Afor each section, in a singlecontainer, treating and impregnating'said sections in .said containerand finally testing the com-' pleted unit at a voltage suficiently highto cause the rupture of one or more of the individual fuses. l

8. A fused, sectionalized, impregnated electrostatic condensercomprising a plurality of sections, an individual fuse for each section,an impregnating fluid surrounding said fuses and said sections, and asingle container permanently containing said im regnating fluid and theentire assembly o conm denser sections with their individual fuses,

the number of sections being somewhat larger than the number ofoperative sections finally desired to obtain the ratedkcapacity,characterized by the fact that, upon a failure of a relatively smallnumber of sections, the remaining sections provide an operating capacityWhich does not vary materially from the rating desired.

In testimony whereof, I have hereunto subscribed my name this 4th day ofJune, 1926.

l RALPH E. MARBURY.

